lava in glazes

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Does anyone have experience using crushed lava in glazes? I have seen the "fat glazes" pots from Germany and that is not what I am aiming for. I've been told lava fires at 1100 fahrenheit; is that correct? and how/is it possible to add color to lava, which I assume fires to black glass.

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i can't comment on "lava" being used in glaze, but for sure pumice is used in glaze. i guess you could call it "lava" since it's volcanic rock.

if you're trying to get the textured effect many of those glazes have, you can experiment with adding silicon carbide to your glaze; which volatizes in the glaze and forms those craters. look up "crater" glaze recipes for more info.

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Does anyone have experience using crushed lava in glazes? I have seen the "fat glazes" pots from Germany and that is not what I am aiming for. I've been told lava fires at 1100 fahrenheit; is that correct? and how/is it possible to add color to lava, which I assume fires to black glass.

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Of 'lava' you can use, volcanic ash and volcanic stones ... 2 different sources and formations. I have experience with both, but as with many materials and firing processes, my notes won't help, sorry. Just follow the scientific process and you should be fine. Just like a lot of materials, if you do find something you like, buy enough to suit you for a long time, as from batch to batch it can easily change. Some volcanic sources are high in silica, others aren't ... only a chemical comp test can tell you and is not worth the money. Most importantly,

first test, crushed rock in kiln, second test, crushed and ball milled in kiln, third test crushed, ball milled, then sifted with fine particles tested. .... these are your base lines of what properties the material has by itself.

next, start to base glaze tests on that material. try to limit materials to your basic base blends of flux, glass former and clay to make something stable, then go for the glaze effects to make the most out of your volcanic material.